preeoe



(No Model.) 2 Sheets-Sheet 1.

W. H. PRBEGE.

TELEPHONE EXCHANGE SYSTEM.

Patented Apr. 28, 1885.

(No Model.) v 2 Sheets--Sh eet ,2. W. H. PREEUE.

. TELEPHONE EXGHANGE SYSTEM.

No. 316.911. Patented App. 28, 1885.

wwmowo 34400441706 40, mlliamflfreece,

N. FETEIHS, Pmw-Lnm m-u. Washington. D c,

Tarts PATENT WILLIAM HENRY PREECE, OF LONDON, ENGLAND.

'SPECIFTCATION forming part of Letters Patent No. 316,911, dated April 28, 1885.

(No model.)

T all whom it may concern.-

Be it known that I, WILLIAM HENRY PREEOE, asubject of the Queen of Great Britain, residing in the city of London, England, have invented certain new and useful Improvements in Telephone-Exchange Systems, of which the following is a specification.

My invention relates to apparatus employed for establishing telephonic intercommunication between the different subscribers in an electric telephone system. The invention relates particularly to the so-called single-line telephone-exchange system.

The object of the invention is to provide convenient means for indicating at the central otfice the calls of the various subscribers; to insure that a clearing-out signal shall be given to the exchange operator at the termination of a conversation between any two subscribers whose lines have been connected; and, also, to provide convenient means for conversing directly through intermediate stations.

The invention is based, generally, upon the employment of permanent electric currents traversing all the subscriber-lines and acting upon corresponding indicating devices at the central station in such a manner as to indicate the condition of each line. When the telephone-receiver of any given subscriber is at rest or not in use, a weak current flows continuously over that subscribers line to the central station. A galvanometer or other equivalent device included in the circuit of this line at the central station indicates the presence of the current; When, however, the telephone- When two subscribers are placed in direct I connection with each other, an indicator at the central office iscOnnected with the throughline thus formed by means of a branch or leak conductor extending to the earth through a suitable artificial resistance. So long as the two subscribers are in communication with each other the batteries from which the permanent currents are derived are disconnected from the main line, and the leak is of such high resistance that it offers no material interference to telephonic communication. When, however, the conversation between the subscribers has ceased, and one or the other of the receivers is placed upon its bracket, the corresponding battery sends a current over the line. This currentactuatesanindicatonwhich is placed in the leak-conductor at the central office, and thus affords a signal whereby the central operator is informed that the conversation has been concluded and that the apparatus at the central station may be returned to its normal position.

In instances where it is necessary to connect an intermediate office in the line. suitable switch devices are employed, whereby a single telephone at the intermediate office may be employed for communicating with both sides of the line. Suitable inductors are also provided for showing from which section of the line the call is sent.

The call for the intermediate office, and also, if it is so desired, for the central office, may be given by means of a current of increased strength instead of by an interruption of the current normally employed,

In the accompanying drawings, Figure 1 is a diagram illustrating the general organization of apparatus, including the central station, a subscriber station, and an intermediate station or ofiice. Figs. 2 and 3 are diagrams illustrating the different positions of the switch employed at the intermediate office; and Fig. 4 illustrates certain details in the construction of the apparatus.

Referring to the drawings, L, L, L and L represent four subscriber-lines of a telephoneexchange system. Each of the lines L is equipped with the usual telephonic transmitting and receiving instruments, B and C, respectively. The receiver Ois intended to normally hang upon abracket, D, which also constitutes a switch. This bracket consists of a lever, d. A contactpoint, d, against which the pivoted arm at rests when the telephone receiver is supported thereby, is connected by a conductor, 1, through a suitable indicating device, E, with a conductor, 2, and the conductor 2 leads to one polesay the positiveof a battery, 0. The negative pole of this bat tery is connected by a conductor, 3, with the earth at g. The lever d is connected by a conductor, 4, with a contact-point, f, of a switch or circuit-interrupting device, F. The device F consists of a lever, f, playing between two contact-points, f and f When the lever f is pushed forward, it is moved out of contact with the point f and into contact with the point f The point f is connected through a conductor, 5, with the positive pole of a supplemental battery, 0 The negative pole of this battery is connected through conductors 6 and 7 with the positive pole of the battery O. The lever f is itself connected with the main line L leading to the exchange office.

The lever cl is equipped with a contact-point, d against which it impinges when the tele phone-receiver is removed from its bracket. The point d is connected by means of a conductor, 8, in which is included the receiver 0 with the secondary wire h of an induction coil, H. The other terminal of the wire h is connected by a conductor, 9, with the earth- I), of the lever d. A contact-point, d, is applied to the pointld and against this the point d impinges when the lever is relieved of the weight of the telephone. The point d is connected by a conductor, 1l,with one pole-say the negativeof the battery 0 and the positive pole of this battery is connected, through the conductor 12, with the remaining terminal of the coil h.

Between the conductors 11 and 2 there may be inserted a supplemental battery, 0, for the purpose of increasing the amount of battery sent to line when the switch F is operated; or the conductor 5 may lead directly to the earth.

It will be seen that when the receiver 0 is removed from its bracket the indicator E will be taken out of circuit, while the transmitter B and receiver 0 will be placed in circuit and the connections of the battery 0 will be com pleted through the primary of the inductioncoil H. The interruption of the circuit of the battery 0 is employed for operating an indicator, E, at the central station, thereby showing that the subscriber upon the line L wishes to be placed in communication with another subscriber.

At the central station each main line is led to a corresponding spring-jack, K. Each spring-jack of this series consists of two plates, is and one of which is flexible, and permits of the insertion of a switch-plug, k. The main line preferably leads to the lower plate, 7.0, while the upper plate, k is connected with a corresponding galvanometer indicating device, E, E, E or E. This organization is shown in connection with the conductor L by means of the conductors 13 and 14, the conductor l4 leadingito the earth from the indicating device.

So long as a current traverses the subscriberline L, for instance, it passes from the lower plate, is, to the upper plate, 70 of the spring-jack, thence through the indicating device E to the earth. The current traversing theline causes the needle 6 to be deflected in a given direction say to the left hand-therebyjlindicat ing to the operator that the line is in its normal condition of rest. Whenever the subscriber whose instruments are connected with the line L, for instance, removes his receiver from its support, the interruption of the current causes the needle to move to its central position, as shown at 6, thus indicating to the exchange operator that the subscriber has sent in a call.

For the purpose of causing the call to remain, even though the subscriber should return his telephone to its bracket, an annunciator, I, is employed. Such an annunciator consists of an electro-magnet, t the poles of which are presented to the lid i. The lid is pivoted at its lower edge in such a manner that it will tend to fall forward. The normal magnetization,however,of the electro-magnet, which is caused by the permanent current, is sufficient to hold the lid toward its poles until upon the cessation of the current the lid is released. For the purpose of rendering the instrument as compact as possible the galvanometer-needle is preferably placed in the same instrument with the annunciator-lid, the latter being cut away through its upper portion for the purpose of exposing the needle. When the central operator has thus received a call from a subscriber, he places the switch-plug it into the spring jack corresponding to the line. The switch-plug isinsulated upon its one side, while the other side is connected through the corresponding cord N with suitable telephonic transmitting and receiving instruments, such asshown at B and G, respectively. The main line L is thus connected when the switch-plug is placed in the, springjack through the instruments B and O with the earth. The central-office operator upon learning the requirements of the subscriber proceeds to connect the line of the calling subscriber with that of the person desired, and this he accomplishes in a convenient manner by means of a double switchcord, N. This cord is provided with plugs k and le the one of which, k is placed in a spring-jack, K, while the other is placed in the spring-jack K, for instance.

The doublelswitch-cord N is connected with the earth through an indicating device, E. This device preferably consists of a galvanometer similar to the device E, which, so'long astwo lines, L and L, are connected with each other and the subscribers connected with the same are in conversation, stands in a given position. Whenever either or both subscribers replace their instruments, a current is sentfrom the corresponding battery to the main line, and this current serves to move the galvanometer-needle, thus indicating the cessation of the conversation between the subscribers.

,, e For the purpose of rendering the resistance may be connected with a conductor, 17, lead ing to a cabinet, as indicated at N. In this cabinet suitable telephonic instruments are placed. 'Such an organization is especially desirable where telegraphic messages are to be received by telephonic communication.

In some systems it is necessary to connect the subscribers lines through intermediate stations, and in such organization a slightly different organization of apparatus is employed. In connection with the main line L such an organization of apparatus is shown. The main line L is shown as divided into two sections, Z and P. The section Z proceeding from the subscribers station is connected with a switch device, F, similar to the device F. .The resting contact f of the switch F is connected through an indicating device, E, with aswitch-point, p, of aswitch device, 1?, by means of a conductor, 18. The lever f of the switch F is connected with the section Z of the line L. The back contactpoint, f of the device F is connected, by

means of a conductor, 19, with one pole of a' battery, 0, the opposite pole of which is connected by a conductor, 20, with the earth at The switch device P isprovided with eight contact-points, as shown at p 19 19 &c. This device is provided with a switch-handle, g, which may be moved into either of three positions, the several positions being represented in Figs. 1, 2, and 3, respectively. When in theposition shown in Fig. 1, the point p is connected with the point 19 the point pwith the point 10 and the point p with the point p. A conductor, 21, leads from the point p to the lever d of a telephone-supporting device, D',which is similar to the device D, already described. The resting contact-point d of this lever is connected by a conductor, 22,'with the point 19 When, therefore, the switch P is in position shown in Fig. 1, the connections of theline L are through the point p, t0 the point p, thence through the i lever d and conductor 22, to the point p and thus through the point p with the point p". This point p is connected with the portion Z of the line L, leading to the central ofiice.

The front contact-point, d ,of the telephoneswitch D is connected by a conductor, 23, through the receiver 0 to the secondary coil 72. of an induction-coil, H. The remaining terminal of this coil h is connected by means of a conductor, 24, with the point p. When, therefore, the instrument 0 is removed from the bracket D, the connection of the incoming line from the lever d is interrupted at the point 66, and is completed at the point d through the conductor 23, including the telephonic instruments, to the point p, and thus to the section Z of the line L leading to the central station. The telephonic instruments B and G are thus placed in connection with the main line L at an intermediate point. The primary coil h of the induction-coil H is connected in circuit, through a transmitter, B, with the respective poles of a battery, 0.

For the purpose of placing the switch P and the apparatus at the corresponding station in such position that a call may be received from either direction when the apparatus is not in use, the arm q is moved into the position shown in Fig. 2. By so moving the switch-arm the point p is placed in connection with the point p, the points 19 and p are connected with each other, and likewise the points 12* and p and p and 10 The point p is connected, through a conductor, 28, with the earth at 9 The connections from the section Z of the line L are from the point p to the point 19 thence through the lever d to the point p, and thence to the point 19 The point p is connected, through a conductor, 25, with one pole of a battery, 0. The remain-. ing pole of this battery is connected with the earth at g by means of a conductor, 26. An indicating device, FF, is included in this conductor 25 for the purpose of receiving indidications from the section Z of line L leading from the central station. A suitable resis tance, T may also be included in this con- :ductor.

If, when the switch is in the position last described, the instrument 0 be removed from its support, the connection from the point 10 will be changed so as to be connected through the point d and the telephonic instruments 0 with the point 10 and thus through the point p with the earth at 9 The telephonic instruments will thus be placed in connection with the section of the main line leading to the central oflice, and the indicating device B will be cut out of circuit. So long, however, as the instrument 0 is in use a positive current will be sent from the battery 0 to the main line leading to the central office in precisely the same manner as is otherwise tion.

The third position in which the switch P point 01, and through the conductor 22 to the sent by the battery 0 at the subscribers stamay be placed is shown in Fig. 3, in which the point p is connected with the point 105, the point p with the point 12 and the point p with the point 19 The connections of the sections of the line L leading from the subscribers station are then complete through the instrument E to the point p, as usual, thence through the point 19 and conductor 22 to the point (1, thence through the lever 01 and points 19 and p and conductor 24 to the earth at The remaining section Z of the line leading from the central office is at the same time connected from the point p to the point 19 thence through the conductor 25 and instrument E to the battery 0, from this battery to the earth at the point The instrument is now in a position of rest, and both sections of the main line are connected at the intermediate station with the earth through their respective indicating devices. If, however, it is desired to communicate from the intermediate office to the central office, the arm q of the switch device P should be moved into the position shown in Fig. 2 for the purpose of preventing the section of the line L leading from the subscribers station from being leftwithout a groundconneotion when the instrument 0 is raised from its suport. p When a subscriber is temporarily absent from his office, a convenient means of indicating the fact at the central office consists in using a reversing-switch, such as shown at S, for the purpose of transposing the connections of the battery from which a current is normally sent to line, so that instead of a positive current a negative current will be sent. The position which the needle of the galvanometer corresponding to that line at the central station assumes will indicate to the central operator that the battery has been reversed and that the subscriber is not within calling distance.

I have shown the contact-point of the device F as connected with the pole of the battery 0 so that when the device F is operated a weak negative current is sent to line. This may be employed for actuating a bell, U, at the subscribers station, such bell being adjustcd to respond to the current'from the battery 0 alone, but only to the additional current which is thus sent to line.

I claim as my invention 1. The combination, substantially as hereinbefore set forth, of a telephone central office, a series of subscriber lines radiating therefrom, a battery applied to each of said subscriber-lines, from which a current is normally'transmitted to the corresponding line, an indicator included in the circuit of each of said lines, and means located at the central ofiice for. automatically interrupting such current when the transmitting-telephone is in use.

2. The combination, substantially as hereinbefore set forth, of a. central station, aseries lines with each other, an earth-connection.

which is completed at the central station when such lines are so connected, and an indicator in said earth-connection.

3. The combination, substantially as hereinbefore set forth, of a telephone central station, a series of telephone lines radiating therefrom, means for causing an electric current to traverse each of said lines when they are at rest, an indicator in each of said lines which is effected by such current, means for interrupting the current traversing any of such lines and thereby actuating the corresponding indicator, means for connecting any two of said lines with each other, and means for establishing an earth-connection for both of said lines at or near the point where they are so connected.

4. The combination, substantially as hereinbeforc set forth, of a telephone central office, a series of lines radiating therefrom, a galvanometer included in the circuit of each of said lines, a battery applied to each of said lines, means for interrupting the connections of said battery, an earthconductor at the central station. an indicating-galvanometer included in said earth-conductor, means for connecting any one of said lines with anyother and simultaneously placing both lines in connection with the earth through saidearthconductor, and the indicating-conductor included therein.

5. The combination, substantially as hereinbefore set forth, with a telephone central office, of a subscriber-line, a battery for normally transmitting a current upon said line, and an indicating device included in saidline, which device consists of a galvanometer, an electro-magnet, and an annunciator-lid, said lid being cut away through its upper portion to disclose the galvanometer-needle.

6. The combination, substantially as hereinbefore set forth, of a telephone main line, a battery for transmitting an electric current upon the same, a device serving to indicate the presence of such current, means for automatically interrupting the current when the line is in use, and means for reversing the connections of said battery with reference to the line at will.

7. The combination, substantially as hereinbefore set forth, with a telephone central office, a subscribers station, and an intermediate office, of a subscriber-line leading from the subscribers station to the intermediate office, a line leading from the intermediate to the central office, an indicating device included in the circuit of theline leading from the subscriber sstation, an indicating device included in the circuit of the line leading from the intermediate station, both of which indicating devices are located at the intermediate office,-

ICO

a telephone transmitter and receiver located at the subscribers station, like instruments at the intermediate office, means for transmitting a current upon the subscriber-line when the 5 first-named instruments are at rest, means for interrupting said current When the instruments are in use, and a circuit-changing device at the central station, whereby the connections of the subscriber-lines may be completed with the exchange-line either directly or through the telephonic instruments located at the intermediate office while the earth-connections of said lines are interrupted at the intermediate office.

8. The combination, substantially as hereinbefore set forth, of the line L, consisting of the sections Z and P, the conductors24 and 25, the indicating devices E and E respectively, included therein, the levers D and 1), means 20 for normally completing the circuit-connecsaid sections with each other, either directly or through the receiver 0.

In testimony whereof I have hereunto subscribed my name this 21st day of October, A. D. 1884.

WILLIAM HENRY PREEGE.

Witnesses:

, .DANL. W. EDGECOMB, CHARLES A. TERRY. 

